If every motorist caught during the three week warning period had paid the full fine, they would have paid out £270,000.

A network of six static cameras and a mobile detection vehicle are now fully operational across Belfast.

The Department of Regional Development insists the enforcement measures are “aimed squarely at the drivers who illegally use bus lanes to jump queues and cut across traffic”.

They added: “These drivers can be a hazard to themselves, other road users, cyclists and pedestrians. They can also delay the progress of passengers opting to use our public transport service.”

The fine is £90, but will be reduced to £45 if paid within a 14 day period. There will be a right of challenge for any driver who considers the fine has been incorrectly issued.

Roads Minister Danny Kennedy defended the fines yesterday.

He said: “At the beginning of June I introduced measures to reduce the number of drivers illegally using bus lanes.

“To help drivers realise that if they ignored the restrictions they would risk a fine I applied a three week ‘warning period’ when offenders would receive a warning letter. That ‘warning period’ has now ended.

“The advice is simple, observe the bus lane restriction and avoid the likelihood of a fine.”

The Department has six fixed enforcement cameras in operation in Belfast City Centre - at Castle Street, East Bridge Street, Donegall Square East, Donegall Square South, Great Victoria Street and College Street East. A mobile camera unit is also enforcing the bus priority measures across the greater Belfast.

DRD says all bus lanes, along with their operational times, are clearly identified and are already a familiar feature to drivers.